1. Field of the Invention
The present invention relates to a probe of a semiconductor socket, which is applied during a semiconductor package test to test an electrical characteristic of an integrated circuit in a semiconductor package called, for example, BGA (Ball Grid Array).
2. Description of the Related Art
In a semiconductor package, a semiconductor chip on which semiconductor integrated circuits are formed is packaged through a package sealing process using, for example, a resin. As one of the semiconductor packages formed by the way described above, a BGA package 1 shown in FIGS. 6(a) and 6(b) is known. On a bottom surface of the BGA package 1 are placed solder balls 2 serving as an input/output terminal from or to an outside and which are arranged in a grid form.
In order to carry out a test on semiconductor integrated circuits mounted in the BGA package 1 to check their electric characteristics, a semiconductor socket 4 in which a plurality of probes 3 are mounted, is provided as shown in FIG. 7. That is, at a time of making the test, by mounting the BGA package 1 on the semiconductor socket 4, the solder balls 2 come into contact with contact terminals 5 placed on the probe 3. Since the contact terminals 5 are provided with elasticity by a compressed spring (not shown) being placed in a lower portion, an effective contact between the solder ball 2 and the contact terminal 5 can be obtained.
However, each of the contact terminals 5 placed on the conventional probes 3 has a tip portion 6 as shown in FIG. 8. The end portion 6 is configured in a manner that it has four projected portions each having a crest. Therefore, since the conventional probe 3 comes into contact with the solder ball 2 at four points, the solder ball 2 is scratched. As a result, if the BGA package 1 is mounted on a print substrate after the test has been completed, there is a risk of occurrence of a junction failure. Thus, the conventional probe 3 has a disadvantage in that an increase in defective rate of the semiconductor package is unavoidable.
Moreover, if the four crests on the end portion 6 come into point-contact with the solder ball 2, pushing force is concentrated in the point-contact position of the solder ball 2. Therefore, solder separated from the solder ball 2 easily sticks to the end portion 6 and, due to oxidization of the stuck solder, a rate of occurrence of contact failures becomes high. On the other hand, the end portion 6 of each of the contact terminals 5 is crushed in a short time and becomes unusable and a frequency of replacing the contact terminal 5 becomes high. The above problems occur often when the solder ball 2 is formed using a Pb (lead)- free solder.
In view of the above, it is an object of the present invention to provide a probe for testing on a semiconductor package which is capable of reducing scratching on a solder ball, sticking of solder to a contact terminal, and damage to the contact terminal.
According to a first aspect of the present invention, there is provided a probe applied to semiconductor package test which is to test an electrical characteristic of an integrated circuit in a semiconductor package, having:
a contact terminal to contact electrically a solder ball serving as a contact of the semiconductor package;
wherein the end portion of the contact terminal is provided with: a concave portion which is to come into contact with the solder ball and has a concave showing almost hemispherical shape; and at least a guiding groove to guide adherent solder adhering to the concave portion from the solder ball to outside, which is formed on the concave portion and extends from the bottom center of the concave portion toward outside.
With the above configuration, the contact terminal employed in the probe for testing a semiconductor package has almost semispherical concave to be in contact with the solder ball in the semiconductor package and a guiding groove being formed from a center of the concave portion in a direction of a diameter and operated to guide solder adhering to the concave portion. As a result, since the solder ball comes into contact with the contact terminal not in a point contact form but in at least a line contact form, an amount of solder adhering to the concave portion can be reduced. Thus, the scratch on the solder ball and the damage to the contact terminal can be minimized. Therefore, a junction failure of the semiconductor package occurring when the semiconductor package is mounted and additionally a life expectancy of the probe can be lengthened. Moreover, since the solder separated from the solder ball and adhering to the concave portion flows out along the guiding groove from a center of the concave to an outside of the contact terminal, a long washing period to be used for removing the solder can be secured. Therefore, an operation rate of the test apparatus can be improved.
In the probe, the contact terminal may be made up of a cylindrical body having said end portion and having a diameter being slightly smaller than that of said solder ball.
In this case, by making a diameter of the contact terminal slightly smaller than the solder ball, pushing pressure is not concentrated in a point contact position of the solder ball but is dispersed in a face surrounding the solder ball and therefore an amount of solder separated from the solder ball and adhering to the contact terminal can be further reduced.
According to a second aspect of the present invention, there is provided a method for testing an electrical characteristic of an integrated circuit in a semiconductor package, for making a solder ball serving as contact of the semiconductor package contact electrically a probe putted in a test semiconductor socket, comprising:
placing the solder ball into a concave showing almost hemispherical shape of a concave portion formed on a contact terminal of the probe;
making the solder ball contact the concave portion;
guiding adherent solder adhering to the concave portion from the solder ball to outside by at least a guiding groove formed on the concave portion.